Rain cone holding water

[stewartwlewis]

I have had a Davis VP2 for over 9 years and earlier this year I had to replace the rain bucket reed switch. Since then I have been concerned about rain accuracy so decided for piece of mind to buy a new rain spoon and also replaced the cone with the new design with bird spikes. Since then the station seem to miss rain when its light.
A couple of days ago when it had been clearly raining and my site was showing no rain I checked the station and the inside of the cone was full of very large water beads and the water seemed to be pooled across the screen at the bottom due to surface tension. I carefully ran my finger round the inside of the cone dislodging the beads and this resulted in two spoon tips showing 0.4mm of rain. The rain had stopped and I think all of the moisture would have evaporated had I not dislodged it.
The surface of the new cone seems to hold on to water rather than repel it.
Should I have treated/washed the inside of the new cone before installing it?
I have read about coating with RainX (for plastic), pledge, car wax…. Is it worth doing?

[Phil23]

Don't recall my experience of using RainX 20+ years back on the car.

Would assume a wetting agent on surfaces would help as it would help break the surface tension of the water drops & pool in the strainer.
I'd expect it would eventually/Quickly wash away though.

Any waxing might help it run down the cone, but it's still gonna bead in the strainer.

(Making it up as I Go).....
The other thing that might help could be a couple of loops of cotton in the strainer with the end hanging thru; cotton should get wet & let the water wick thru.

Cheers.

[prodata]

I don't imagine the RainX would do much harm, though it's not an official recommendation.

TBH if the new cone etc really is pretty new then I'd be inclined to leave it. Whatever the surface finish of the cone is, it seems to encourage beading more when it's brand new. But after weathering in for a while, the surface seems to revert to more the expected run-off behaviour. You're always going to get an element of micro-beading but it typically wouldn't be more than one tip.

[stewartwlewis]

Thanks Phil, got the new cone from you John (bought 21 June) and I am sure the new surface will end up like the old one at some time in the future but in the current weather conditions its missing about 0.4mm of rain every light shower.
This subject had been discussed a while ago but I couldn’t find much from people that had actually tried coating the cone. Since I now have a spare rain cone, I thought I would have a go myself.
I don’t think waxing or other car surface treatments are the way to go as they just create beading and I have lots of that already. So that leaves RainX, NeverWet or WD40!
RainX gets mixed reviews elsewhere (not weather station related) but I haven’t seen anything on NeverWet.
Bought some in Homebase at a third of the Amazon price and it’s amazing, tested on cardboard and water just runs off. So on with the test.
Photo 1 – Baseline, this is the old cone left out to get a bit wet in todays drizzle. No beading and water just oozes down the hole.
Photo 2 – New cone as is with debris trap. Large beads all over the cone and small puddles actually in the debris trap.
Video 3 – Old cone treated with NeverWet, slow motion video of water being sprayed onto the cone. Water forms spheres and rattles down the hole. Had to be slow motion as it moves off the surface very fast and it just looks great.
Video 4 – New cone water sprayed – no need for slow motion here. Water just beads on surface until droplet gets too big, runs down and then gets trapped by debris screen.
Photo 5 – Old treated cone during one of today’s spells of drizzle. Almost no water on the inside of the cone.
Photo 6 – New cone during the same drizzle spell. Lots of water adhering to the inside of the cone and debris trap.
Photo 7 – New cone an hour and a half after drizzle stopped. Lots of water still adhering to the inside of the cone and evaporating away.

Interim conclusion is it works! Rain entering the cone gets to the tipping spoon and doesn’t get stuck on the sides.

This has not been an empirical side by side test as I don’t have anything to measure water volume accurately enough but I am not testing the actual measuring capability of the Davis device, I trust it measures what gets to the tipping spoon correctly, this is about getting the rain to the spoon.

I am going to leave the old cone on the weather station for a bit and see how well the treatment continues to work. The manufacturers claim is it is only damaged by wear, high pressure water, detergents and solvents/oils and the inside of a weather cone should be free from all of those things.

I do wonder how well NeverWet will work on the debris screen but I will think about treating that and the new cone later! I have left the new cone outside John to see if it loses the current beading properties.

Photo’s in this link
https://photos.app.goo.gl/SMyu3CunoA1ezfFT8

[rogerthn]

Thanks for sharing Stewart!
Since my old Oregon PCR800 only counts full mm I cannot really compare it with my new ECOWITT WH40 that counts 0.1 mm but there are some beads in the cone.
So far the ECOWITT WH40 does show more rain but if there is a day with very little rain both will show 0
Rain rate right now, according to the WH40 4.2

[stewartwlewis]

Hi Roger
The cone on the WH40 looks a lot less steep than the one on the Davis. I was quite surprised how much water actually adhered to the sides, if the WH40 cone had the same sort of finish you would get puddles with that angle!
It would be a lot easier to apply NeverWet though as the overall shape is flatter but I wonder if you would lose a lot of rain in a wind or very heavy shower. Water does almost bounce off the coating. One saving grace, the leaflet with the product does say it can be removed with a light sand followed by a wipe with white spirit.
No rain today, so no testing but that’s not going to last long.

[rogerthn]

As seen on https://rogerthn.se/weather2/index.htm and https://rogerthn.se/weather3/index.htm
PCR800 = Rainfall Last 24 Hours 14.5 mm Last rainfall 2020-07-05 17:12
WH40 = Rainfall Last 24 Hours 14.3 mm Last rainfall 2020-07-05 17:53
Maybe I'll get some RainX but there seems to be more than one Rain-X

[sfws]

You might want to read - viewtopic.php?f=16&t=16772&p=128864&hilit=beads#p128864 and viewtopic.php?f=42&t=18029&p=142485&hilit=beads#p142485 where (non Davis) similar issues are discussed, you may find more if you type "beads" into search box.

[stewartwlewis]

Thats proper rain. I have only had two days above 10mm since February. Durham UK is in the rain shadow of the Pennine hills and most of the rain I get is what’s left of the fronts from the Atlantic. Hence the requirement to capture all the drizzle!
I looked at RainX and it's website suggests that its designed to bead rain on glass windscreens or with the plastic version plastic visors, just as wax does on a cars body work. As the car moves these beads of water are blown off leaving a clear windscreen. NeverWet is supposed to create water spheres that run off the surface. I already have lots of beads, hence opting for Neverwet.
Interesting test today, old cone with NeverWet is on the weather station, new Davis cone is on the ground with a yogurt pot below it. Quick shower of rain and the station with treated cone registered 0.4mm of rain. The yogurt pot below the new cone is completely empty, all the rain is beaded on the outside of the cone.

Thanks swfs, reading through all the “beads” stuff, leaving a new cone to have it’s coating removed by "the elements" is very understandable but it’s probably going to take a while and to be honest if I had just bought my first quite expensive weather station I would be a bit disappointed if (what is if you are out in it) material rain, was not being recorded.
I guess my advice to people with a new weather station would be to spray the inside of the cone with some sort of degrading wetting agent such as WD40 or silicone spray. Testing to be done this week as I have both. Now just have to work out the weight of water that should be in the yoghurt pot for each 0.2mm.
The NeverWet coating is a bit of fun but actually seems to be working well.

[mcrossley]

Don't use WD40 - it's an oil and any dust, muck, passing feathers etc will adhere to it.
Neverwet degrades in UV unfortunately.

I have tried repellent finishes including RainEx and though they work for a while, I found that when the plastic weathers to a matt finish it works fine, the water spreads and flows down under gravity just fine - and no maintenance required other than the odd wipe out.

[rogerthn]

Don't use WD40 - it's an oil and any dust, muck, passing feathers etc will adhere to it.
Neverwet degrades in UV unfortunately.

I have tried repellent finishes including RainEx and though they work for a while, I found that when the plastic weathers to a matt finish it works fine, the water spreads and flows down under gravity just fine - and no maintenance required other than the odd wipe out.

Thanks!
Since I don't have any Neverwet or RainEx at home I was tempted to try some WD40 but I'll now let the weather ( ) and time do the work

[Phil23]

If you are up for another video experiment, a light wiping with a diluted detergent would be interesting.

I know ultimately it's gonna rinse off, but would be an interesting exercise still the same.

Phil.

[Mapantz]

Personally, I would stay away from using anything on the Davis rain gauge. The only thing I would probably do in the OP's position is use a scouring pad and gently run it around the cone to rough the surface up.

I did try out a silicone spray on my Ecowitt gauge, but I noticed several problems occurring. One was bounce-outs of large rain drops, another was erroneous rain rates because during heavy/torrential downpours, the water tended to 'spiral' for too long and then suddenly dump a load of water in to the tipping mechanism - it just didn't give realistic values.

When I upgraded to the Aero cone, mine certainly didn't bead up like that. If accuracy is your thing i'd stay clear of water repellents. I suspect the Met Office don't go around spraying their manual rain collectors (or automated ones) with anything.

[stewartwlewis]

I agree with everybody who says you shouldn’t need to coat the rain cone with anything and also agree that the met office certainly doesn’t do that. My original cone (9 years old) didn’t hold any beaded water but the new one does, at least 0.4mm worth on what is an almost vertical surface. That meant on showery days or light rain days I was recording no rain.
So for me what’s needed is a cone with a coating that does no lasting damage and minimises initial beading until the surface weathers or ideally, new cones supplied with an initial surface that doesn’t bead!
The NeverWet coating I put on my old cone seems to be working very well, that old cone didn’t need coating I was just interested to see how NeverWet worked. The steepness and depth of the Davis cone makes bounce out unlikely and the size of the hole in the bottom is designed to stop the gauge from being overwhelmed by rain within it’s specification so for me NeverWet is a good solution. If it wears off through UV exposure and that same exposure gets rid of the current beading surface that would be absolutely great.
As an experiment I have coated the new cone with a silicone spray to see if that would be a better initial coating but yesterday I had 0.2mm recorded on the NeverWet coated old cone and absolutely no water in the yoghurt carton below the new silicone coated .cone.
I have added a short video of the silicone treated cone being sprayed with water (Video 8). The beading looks smaller than the untreated cone and the runoff seems quicker and doesn’t seem to pool so much on the debris screen. Wiping my finger round the beaded and treated cone does however result in 9g of water being dropped into the yoghurt carton. Looking at the advice from Davis 544ml tipped into the funnel (and out into the yoghurt carton) = 1” or 25.5mm of rain. So my 9g (9ml)= 0.42mm of rain. About the same as the untreated cone and for me, not good enough.
Link to photo’s and Videos
https://photos.app.goo.gl/SMyu3CunoA1ezfFT8

[BrianGUK]

I work in the plastics industry, the beading is probably caused by the mould release agent used in the manufacture of the cone.

You can remove it by wiping the cone with 99% IPA.

Hope that helps!